Already, levels of greenhouse gases in the atmosphere are high enough to guarantee climate change for decades, if not centuries, scientists warn in a report by the Intergovernmental Panel on Climate Change. This is in addition to the deadly heat waves, powerful hurricanes and other extreme weather events that are happening now and are likely to get worse.
Describing the report as a “code red for humanity,” UN Secretary-General António Guterres called for an immediate end to power from coal and other highly polluting fossil fuels.
“The alarm bells are deafening,” Guterres said in a statement. “This report must spell the end of coal and fossil fuels, before they destroy our planet. “
The IPCC report comes just three months before a major United Nations climate conference in Glasgow, Scotland, where nations will be under pressure to pledge ambitious climate action and substantial funding.
Drawing on more than 14,000 scientific studies, the report provides the most comprehensive and detailed picture yet of how climate change is altering the natural world – and what may still be to come.
Unless immediate, rapid and large-scale action is taken to reduce emissions, according to the report, the average global temperature is likely to exceed the 1.5 ° C warming threshold over the next 20 years.
So far, pledges from nations to cut emissions have been insufficient to bring down the level of greenhouse gases accumulated in the atmosphere.
Reacting to the findings, governments and activists have expressed concern.
“The IPCC report underscores the overwhelming urgency of this moment,” US climate envoy John Kerry said in a statement. “The world must come together before the ability to limit global warming to 1.5 degrees Celsius is out of reach. “
Reports warn of catastrophic impacts
Emissions “unequivocally caused by human activities” have pushed the current global average temperature 1.1 ° C above the pre-industrial average – and would have pushed it 0.5 ° C further without the moderating effect air pollution, according to the report.
This means that as societies move away from fossil fuels, much of the aerosols in the air will disappear – and temperatures could soar.
Scientists warn that a warming of more than 1.5 ° C above the pre-industrial average could trigger uncontrollable climate change with catastrophic impacts, such as heat so intense that crops fail or people simply die because they are outside.
Each additional 0.5 C of warming will also increase the intensity and frequency of extreme heat and heavy rainfall, as well as droughts in some areas. Because temperatures fluctuate from year to year, scientists measure global warming in terms of 20-year averages.
“We have all the evidence we need to show that we are in a climate crisis,” said three-time IPCC co-author Sonia Seneviratne, climatologist at ETH Zurich, who doubts she will sign for one. fourth report. “Policymakers have enough information. You may ask: is this a significant use of scientists’ time if left unchecked? “
The 1.1 C warming already recorded was enough to trigger a disastrous weather forecast. This year, heat waves killed hundreds of people in the US Pacific Northwest and broke records around the world. Heat and drought-fueled wildfires are sweeping entire cities across the western United States, releasing record emissions from Siberian forests and causing Greeks to flee their lands by ferry.
“Every element of warming matters,” said IPCC co-author Ed Hawkins, a climatologist at the University of Reading in Britain. “The consequences are getting worse and worse as we get warmer. “
The Greenland ice sheet is “virtually certain” to continue to melt. The oceans will continue to warm and surface levels will rise for centuries to come.
Some irreversible changes: report
It is too late to prevent these particular changes. The best the world can do is slow them down so that countries have more time to prepare and adapt.
“We are now engaged in some aspects of climate change, some of which are irreversible for hundreds to thousands of years,” said Tamsin Edwards, IPCC co-author, climatologist at King’s College London. “But the more we limit warming, the more we can avoid or slow down these changes. “
But even to slow climate change, the report says, the world is running out of time.
If the world significantly reduces its emissions over the next decade, average temperatures could rise another 1.5 ° C by 2040 and possibly 1.6 ° C by 2060 before stabilizing.
If the world does not significantly reduce emissions and instead continue on the current trajectory, the planet could see a warming of 2 ° C by 2060 and 2.7 ° C by the end of the century.
The land has not been this hot since the Pliocene epoch, around 3 million years ago, when man’s first ancestors appeared and the oceans were 25 meters taller than they are today.
It could get worse if warming triggers feedback loops that release even more climate-warming carbon emissions, such as melting arctic permafrost or dying out of global forests. In these high emission scenarios, the Earth could roast to temperatures 4.4 ° C above the pre-industrial average by 2081 to 2100.
“We have already changed our planet, and some of those changes that we will have to live with for centuries and millennia to come,” said IPCC co-author Joeri Rogelj, climatologist at Imperial College London.
The question now, he said, is how many irreversible changes we avoid: “We still have choices to make.